Because of their transparency, glass or plastic substrates are used for various purposes. However, these substrates are liable to generate static electricity on their surface, as they are insulators. When the glass or plastic substrates are used, as they are, as face-plates for displays such as cathode ray tube (CRT), fluorescence indication pipe (FIP), plasma display (PDP), liquid crystal display (LCD), etc., rubbish or dust attaches to the surface of face-plate and the images displayed are difficult to look at. Particularly, in the case of LCD, there is sometimes brought about destruction of IC or mismovement.
In a copy machine 1 equipped with an automatic document feeder (ADF) 2 as shown in FIG. 1, paper clogging is sometimes caused by static electricity generated on a platen glass 3 in the course of feeding documents, whereby continuous feeding of the documents can be made no longer.
In the case of plastic substrates, moreover, because of their low surface hardness, the plastic substrates readily receive scratches on their surface, whereby they sometimes decrease in transparency.
With the view of solving such problems as mentioned above, there is proposed a process for forming on the substrates a metallic coating or a conductive inorganic oxide coating by the vapor phase method such as CVD, PVD or vacuum deposition method. The coatings obtained by this process, however, are low in acid resistance and alkali resistance, though they are excellent in transparency and conductivity. Further, these coatings are liable to scratching, because they lack in scratch resistance. Furthermore, vacuum metallizers are needed for forming these coatings and, moreover, there is a limit to an area or shape of the substrate on which the coating can be formed by this apparatus. In the proposed process, the coatings cannot be formed at low temperatures, and a continuous productivity of this process is poor, because the process is carried out batchwise.
In the platen glass having an antistatic effect obtained by the process as mentioned above, the coatings formed on the platen glass was sometimes scraped off by the documents fed by ADF or a rubber belt fitted to ADF. In the platen glass as mentioned above, there was brought about such a new problem that the copying is carried out in higher copy sensitivity, that is, at a gray scale, the portion of the coating scraped off in the manner as mentioned above is printed as a stain on the copy as obtained.
There is also proposed a process for imparting conductivity to substrates by coating conductive paints having dispersed conductive substances in resins on the substrates. The coatings obtained by this process, however, involved such a problem that they are poor in transparency, alkali resistance, salt water resistance, water resistance, solvent resistance and scratch resistance, though they are excellent in conductivity.
The face-plates of displays, in their other aspect, are sometimes desired to have a regular reflection reducing effect (hereinafter called anti-glare), in addition to the antistatic effect, for inhibition of glaring of the plates. In order to impart anti-glare and antistatic effect to the face-plates of displays, the following processes are known. That is, Japanese Patent L-O-P Publn. No. 16452/1986 discloses a process which comprises preheating a face-plate composed of glass or plastics, spraying over said face-plate a colloidal solution of a silicic acid compound such as a partially hydrolyzed silicic ester or the like, a reactive silicon compound such as silicon tetrachloride or the like, or a solution obtained by mixing said colloidal solution with a water-soluble metallic compounds of such metal as platinum, gold, palladium or tin, and forming a finely uneven coating composed of silicon oxide or its hydrate on the surface of the plate, followed by drying and heating.
Further, Japanese Utility Model L-O-P Publn. No. 168951/1984 discloses a process which comprises forming a coating layer on the face-plate by the vacuum deposition or dip coating method from a mixture of tin oxide or indium oxide and silicon oxide or from a laminate thereof.
However, the face-plates of displays obtained by these processes mentioned above are insufficient in anti-glare, and the antistatic effect thereof varies depending upon the ambient temperature or humidity. Under certain circumstances, moreover, resolving power of the displays comprising such face-plates decreased sometimes. Further, the coatings formed are poor in adhesion to the face-plates and easily peel off, liable to scratch because of lacking in scratch resistance, and peel off or flow out, because the coatings are low in acid resistance, alkali resistance, salt water resistance, water resistance and solvent resistance, whereby anti-glare and the antistatic effect of the face-plates could not be maintained for a long period of time.
By way of Japanese Patent Application No. 299686/1986, the present applicant applied for a patent on an invention of a coating liquid for forming conductive coating which is obtained by homogeneously dispersing zirconium oxysalt, silicon alkoxide or its derivative and conductive substances in water and an organic solvent, or a coating liquid which is obtained by mixing the above-mentioned coating liquid with a nonsedimentable silica dispersion and a growth inhibitor. The coatings obtained by heating the substrate coated with these coating liquid at a temperature of higher than 250.degree. C. were found to sufficiently have properties necessary for their performance in the face-plate, such as transparency, conductivity, scratch resistance and the like, but when they are heated at a temperature of less than 250.degree. C., the resulting coatings decrease in alkali resistance, solvent resistance, salt water resistance and water resistance, and hence it was difficult to apply said coatings to plastic substrates. Because of their low stability, these coating liquid came to gel when they are continuously coated on substrates, particularly by transfer printing, thereby involving sometimes difficulties in carrying out continuous coating operation of the coating liquid on the substrates. Further, in order to store these coating liquid for a long period of time, it was necessary to maintain the storage temperature thereof at less than 15.degree. C.
The present invention is intended to solve such problems associated with the prior art as mentioned above.
That is, firstly it is an object of the present invention to provide substrates such as those made of glass or plastics provided thereon with transparent conductive ceramic coatings excellent in durability such as alkali resistance, acid resistance, salt water resistance, water resistance and solvent resistance, and also in transparency, scratch resistance, adhesion and antistatic effect, said coatings being formed by using coating liquid for forming transparent conductive ceramic coating in which dialkoxy-bisacetylacetonato zirconium, partial hydrolysate of silicon alkoxide and conductive substances are homogeneously dissolved or dispersed in mixed solvents of water and organic solvents (the substrates are hereinafter called the coated substrate A for short), and secondly an object of the invention is to provide substrates such as those made of glass or plastics provided thereon with transparent conductive ceramic coatings having also anti-glare in addition to the above-mentioned properties (the substrates are hereinafter called the coated substrate B for short) and processes for preparing such substrates as mentioned above.
Thirdly, an object of the invention is to provide a display in which the coated substrate A has been used as a face-plate.
Fourthly, an object of the invention is to provide a display in which the coated substrate B has been used as a face-plate.
Fifthly, an object of the invention is to provide a copy machine in which the coated substrate A has been used as a platen glass.